"Beyond the penis: Vaginas shaped evolutionary history"

"Researchers studying whales, snakes, and other animals are finding that female sex organs have some of the same baroque complexity seen in males. They now see females as active participants in an arms race, likely evolving more complex genitalia to help control mating and create barriers to forced matings, which in turn leads to male countermeasures. “It’s likely that female form and function drive male form and function,” says Patricia Brennan, an evolutionary biologist at Mount Holyoke College in South Hadley, Massachusetts...

Highly convoluted folds are found in species including the harbor porpoise and bowhead whale, which have relatively large testes—often a sign that each female mates with multiple males. The researchers suggest that the folds may give females some influence over which sperm fertilize their eggs: Like the duck’s corkscrew vagina, the folds create an additional “gauntlet” that the male must navigate to mate successfully, Mesnick says."
http://www.sciencemag.org/news/2016/01/beyond-penis-vaginas-shaped-evolutionary-history?utm_source=sciencemagazine&utm_medium=facebook-text&utm_campaign=beyondthepenis-1950